Test–retest reliability of the oxygen uptake efficiency slope in surgical patients

The oxygen uptake efficiency slope is a measure of cardiopulmonary fitness, that can be obtained from a sub-maximal cardiopulmonary exercise test. It has been evaluated in medical patients but its reliability in surgical populations remains uncertain. We conducted a test-retest study with the aim of establishing the reliability of the oxygen uptake efficiency slope in relation to that of the anaerobic threshold and peak oxygen uptake, in general surgical patients. Twenty-six patients over 60 years old completed two symptom-limited, incremental cycle ergometry tests within 7 days. The mean (SD) anaerobic threshold was 13.0 (3.0) mlO(2) .kg(-1) .min(-1) . There were no significant differences between mean test and retest values of anaerobic threshold (p = 0.50), peak oxygen uptake (p = 0.76) or oxygen uptake efficiency slope (p = 0.42). Reliability coefficients (95% CI) for the anaerobic threshold, oxygen uptake efficiency slope and peak oxygen uptake were 66.7% (45.3-87.9%), 89.0% (81.0-96.9%) and 91.7% (85.7-97.8%), respectively. The oxygen uptake efficiency slope was determined easily in all patients and found to have excellent reliability. Its clinical utility in determining pre-operative fitness warrants further evaluation.